Telephone system.



a N d H. S. TURNER.

TELEPHONE SYSTEM.

APPLICATION FILED JUNE 20, 1914.

Patented Feb. 9, 1915.

mv EHTOR provision of means whereby on hearing the HUBERT S. TURNER, OF SAN DIEGO, CALIFO RNIA.

TELEPHONE'SYSTEM.

Specification of Letters Patent.

Patented Feb, 9, i915.

. Application filed June 20,1914. Seria1No.8 48,22B.

To all whom it may concern:

Be it known that I, HUBERT S. TdRNER, a naturalized/citizen of the United State residing at San Diego, in the county 0 San Diego and State of California, have invented a certain new and useful Improvement in Telephone Systems, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a' part of this specification. I

My invention relates to telephone exchange systems, some features thereof being of particular service in connection with switchboard systems of the central energy multiple type, to which however, the 1nvention is not to be restricted.

My invention has for its broad o jects, first, the provision of means by which a subscriber on initiating a call to the central exchange, receives an audible signal in his telephone receiver, provided the llne wires and his individual line apparatus at the central office are in operating condition; and means by which the said audible signal is stopped as soon as the operators telephonic set is in a talking and listenlng position in relation to the calling subscriber, thus enabling the usual verbal question of the operator, such as, Number please, to be dispensed with,,as the cessation of the sa1d audible signal is the subscribers notification to state the number he desires to be connected with; second, improved means for governing the association of thesaid operators telephonic set with the link connectors that are employed to unite subscribers lines in conversation; third, the provision of means whereby it is impossible for any operator in the exchange to listen in on any. conversation passing between two subscribers, or to connect, deliberately or accidentally, a third subscriber to the said line,

so that he can listen in or interrupt the conversation being carried on; fourth, the provision of means whereby on testing a called for line, the operator and the calling subscriber both receive distinctive audible signals in their respective receivers, provided the called'for line is being rung upon, a conversation taking place upon it, or another subscriber waiting on that line as hereinafter described, the signals for each condition being so distinct from each other as to bc'readily distinguished; fifth, the

f ringing or talking signal or being so mformed verbally by an operator, the subscrlber can,'on request, be so connected to the cal1ed for busy line that while he cannot overhear the conversation carried on or lnterrupt the same, the called for subscribers bell will instantaneously ring as soon as the latters telephone receiver has been 'replaced on its switch-hook, after the completion of a conversation, and on the removal of.-said telephone receiver again telephonic connection will be established between the waiting subscriber-and the formerly busy line; sixth, the provision of means whereby the mere act of placing the calling plug attached to a link connector in the spring jack corresponding to the called for line causes a ringing current to be sent out on the said line, and means whereby if the line is in normal workingcondition, the operator and the calling subscriber will both hear a distinctive audible signal in their respective telephone receivers assuring them that the line called for is in a normal condition and that the subscribers bell has been rung, and means for stopping said ringing current at the will of the operator, and thereafter automaticurrent is instantly cut off the line and the latter connected in a talking position with the calling subscriber and a signal .displayed before the operator at the centnnl telephone exchange when the called subscriber removes his receiver from its switchhook, whether said receiver is removed while the bell is ringing or not; ninth, the provision of improved means of operating the supervisory relays connected to the talk-' ing circuits of the respective link connectors so that the same are more eflicient in operation and will respond whether ringing current is on the line or not, but only when the receiver on a called for line is removed from its switch-hook; tenth, the

provision of means whereby telephonically connected stations of calling and called lines have independent and free control of the line equipment used in initiating calls, re-

gardless of the fact that one or more link connectors employed to connect the lines may be engaged atthetime with the multiple jacks associated with said lines; eleventh, the provision of meanswhereby the ordinary visual pilot signal displayed when any l ne at an operators position is initiating a call is done away with, and instead a means provided whereby the initiation of such a call sounds a distinctive audible signal in the operators telephone receiver, the said signal continuing until the call is answered, and means whereby the said signal is automatically cut off from the operators receiver, provided she is occupied in establishing a connection between two subscribers or talking to one of them, the said signal in such event being automatically transferred to the operators receiver at the position at the left or right and from that position transferred without sounding to another, if that operator is also busy, and if an operator is absent from a position, to antomatically transfer said signal to another position, the direction of such transfer being controlled manually, and means whereby a call initiated at any operators position sounds its distinctive audible pilot signal, eliminating the distinctive transferred signal from another position; twelfth, the

provision of means whereby upon the com-' pletion of a conversation between two subscribers telephonically connected by means of link connectors by placing the respective receivers upon their switch-hooks, all operating and talking currents passing through the link connectors are cut off, it being immaterial whether the operator removes or not said link connectors from the engaged contacts of the respective lines as far as consumption of said currents is concernedj thirteenth, the provision of means whereby a disconnect audible signal will be heard in the operators receiver whenever there is an idle link connector engaged with the spring contacts associated with any line, so arranged that the audible signal denoting a subscriber initiating a call takes precedence over the same; fourteenth, the provision of improved means ofcommutation whereby the current of an alternating current ringing generator is taken oil at the apex of each alternation or half cycle and sent over one limb of a divided circuit and direct current sent over another limb of the same divided circuit at periods alternating with the former.

Other objects will be apparent from the specification.

My invention provides for more rapid handling of connections than has been afforded by other manual or semi-automatic maaaea telephone systems, and provides a means whereby a calling subscriber is enabled to follow the manipulations and confirm the statements of the operator by means of distinctive, audible signals in his telephone receiver.

To all of the above ends the invention consists in the matters hereinafter described and more particularly pointed out in the appended claims.

The various features and advantages of my invention will more fully appear from a description of the preferred embodiment thereof, shown in the accompanying drawing which illustrates one type of a multiple switchboard telephone exchange system to which my invention may be adapted, but to which type of multiple switchboard system I do not wish to be limited.

For the sake of convenience, I have shown in the drawing all apparatus related to the link connectors between the two heavy black lines representing the talking circuit of the said linkconnector and all apparatus common to one operators position at the switchboard is shown above the top heavy line and between the dotted lines. All apparatus common to the left and right adjacent positions connected thereto, is shown at the left and right of said dotted lines, and finally all apparatus common to the entire exchange is shown below the bottom heavy line excepting battery X which may be-co'mmon to the entire exchange or common only to each operators position. ll have shown at A B, two telephone sub-stations, each including. a receiver, a a transmitter, a a switch-hook, a a call bell, a a condenser, a, and primary, a", and secondary a of an induction coil. The elements a and a, being included in a bridge of the telephone line, which bridge is open when the receiver is upon the switch-hook, a and which bridge is closed by the switchhook, a", when relieved of the weight, of the receiver. The elements a, a are included in another bridge permanently continuous with respect to alternating signaling currents, but non-continuous with respect to direct currents.

The type of sub-station outfit shown is one that I have selected for the purpose of illustrating the invention, but it is to be understood that I do not limit myself to the form of sub-station apparatus shown, for it will be obvious as the description of the invention is proceeded with, that the operation of the system does not depend upon the peculiar sub-station outfit shown.

The stations A B are connected to the exchange in the form of the invention shown by means of metallic circuits, whose limbs C D and C l) are connected with the line springs or talking contacts of spring jacks E, E and F, F. A plurality of 'cut-out relay G, the limbs of each telephone line being normally connected by means of said armature switches and the contacts normally engaged thereby with a line relay H, the limb (1 being connected with thele ft handwinding and brush of commutator I and said commutator I connected to the live pole of the grounded battery K, and the limb D being connected through the right hand winding of line relay H to ground. The line relay H is actuated by the removal of the telephone re-- ceiver at a calling station from its supporb ing switch-hook by means of a circuit which may be traced from transmitter (13, through line C,"left hand armature switch and normal contact of cut-off relay G, left hand winding of line relay H to the live pole of grounded battery K by means of commutator I and-its brush to ground and through the right hand winding of line relay H, right hand normal contact and armature switch of cut-off relay G, line D, Primary a, switch-hook a back to transmitter a As the current passing through this circuit is of a pulsating character, due to the 1ns'ulating segments of commutator I, an alternating current is set up in the secondary a", which is heard as an audible s gnal 1n receiver a by means of a circuit which may be traced from the upper terminal of secondary a", through condenser a, transmitter a switch-hook a? and its left hand contact, receiver a back to the lower terminal of secondary a. This audible signal being heard by the calling subscriber assures him that his line wires are in working condition and that his line signal operating mechanism at the central exchange has operated properly. It will be noted that the brush of commutator I is also connected to the live pole of grounded battery K by means of resistance 6 which is such that it is suflicient to prevent the complete interruption of battery current through the windings of line relay H, when the brush of commutator I is engaged with one of the insulating segments of the same, but which does not prohibit the production of a pulsating current in the circuit, including primary a, owing to its resistance being much greater than that represented by commutator I and its brush. The commutators Q and Z are similarly equipped with a resistance shunt. Therefore, any circuit connected to commutator I, Q or Z, will receive a current which while pulsating in character, is not intermittent, and in this way the relays connected to said circuit are maintained in an actuated condition.

When line relay H is actuated, as hereinbefore described, its armature switch closes a circuit which-may be traced from the ground connection of said armature switch through its contact, line lamp or signal k line'h primary of operators induction coil h at the central operators position,-left hand winding of pilot relay L, line It, and

the live pole of grounded battery K, by

means of commutator I and its brush back to ground, it being understood that said primary and winding are common to a group of line lamps or signals 72, and in the case of a divided position, this group would'constitute all the line signals on the left side of the position, and in the case of an undivided position it would constitute all the line signals thereat. By this means, line lamp or signal It is energized by the pulsating current produced by commutator I, and at the same time an alternating current is generated in the secondary of induction coil 12, by the pulsating current flowing through the primary of the same. A circuit for this alternating current may be traced from the lower terminal of the secondary of induction coil k through armature switch m of operators relay M, armature switch m, normally engaged with it, left hand spring switch of operators spring jack m sleeve m of operators jack plu operators receiver m, tip m of operator s plug, middle spring switch of operators spring jack m inner left hand normal contact and armature switch of operators relay M and common return line m, to the upper terminal of the secondary of induction coil h thus an audible signal is produced in the operators receiver at the particular position assigned to answer calls of the line in question.

In the preferred embodiment of my invention, I take all the line lamps located with their jacks on the left hand half of each operators position and connect same as hereinbefore described, to primary of induction coil h While those located on the right hand half of the same arc connected to primary of induction coil it, the said primary being energized and actuated in a precisely similar manner to the primary of induction coil h and whose secondary circuit can be traced from the lower terminal of the same through the right hand armature switch and normal contact of operators relay M, right hand spring switch of operators spring jack m and receiver m, and back to the upper terminal of the secondary by the same path as that used for the moval of any sub-station receiver from its switch-hook displays a visual. signal and atthe same time causes a distinct audible signal to be heard in the oper'ators telephone. receiver. lhus I do away with thethat a visual slgnal requires a voluntary action on the part of the operator to observe the same, while on the other hand, the hearing of an audible signal 1s a purely automatic function. 1

The description so far given of an audible pilot signal is applicable only when the operator is not engaged in completing a call or talking to a subscriber. Whenever an operator is so engaged, she is obliged to 1nsert answering plug N in a spring ack associated with the line of the calling subscriber and grasp the metallic thimblen of calling plug N which is mounted on a convenient portion of thebody of said plug, allowing a finger contact device m connected to the winding of operators relay M, to make electrical contact therewith. By doing this, a circuit is closed through pilot relay L and operators relay M, which may be traced as follows: from the live pole of grounded battery K through line is, right hand winding of pilot relay L, winding of operators relay M, finger contact device m, thimble n of calling plug N normal contact of the middle armature switch of the three upper ones of calling relay 0, winding of finger contact relay P, sleeve of answering plug N, thimble of answering jack F, left hand winding of message register V, winding of cut-01f relay G to ground. In this manner, the windings of pilot relay L and operators relay M are energized and pull up their respective armature switches. In this condition, should a line signal operate at the particular position Whose operator is engaged in completing a connection for or conversing with another subscriber and should such line signals and jacks be one of those at the left hand side of the position, then the alternating current generated in the secondary of pilot induction coil if, as hereinbefore described, would follow a circuit which can be traced as follows: from the lower terminal of secondary of pilot induction coil 71., spring switch m and its alternate contact, right hand armature switch of pilot relay L of the-position at the immediate left of the position where the signal has originated, its normal contact, right hand armature switch of operators relay M of said position, its normal contact and right hand spring switch of operators jack m and if the-operators plug is inserted in the said jack, to her receiver and thence by way of the innermost left hand armature switch of relay M, to the common return line 412., to the upper terminal of the secondary of pilot induction coilk in the same manner as has already been described in relation to the pilot signal at the central position. 1 However, if this I operator is also busy, then the right hand armature switch of her pilot relay L is pulled up, disengaging its normal contact and engaging its alternate one, so that the alternating, secondary current from the central position would proceed by way of said alternate contact of pilot relay L to the left tion coil-l2, of the central position by way of the common return line m as has been amply described in relation to the central position. If, however, the operator at the right hand position is absent, the plug connecting her receiver is withdrawn from its jack, whereupon the left hand spring switch of operators jack m engages its contact (which engagement can only be brought about by the removal of the plug attached to the operators receiver), the said contact being connected to the left hand switch lever of hand switch Z whose contact point is connected to the left hand armature switch of pilot relay L of the next position to the right (as is clearly shown in relation to the same switch contacts at the central position). Thus the alternating current generated in the secondary of induction coil 72. is automatically transferred to the next position and'will continue to be so transferred until it reaches the first operators position at the right where there is an operator on duty as exemplified by her receivl'er being plugged into its corresponding ac r.

If the operator at the left hand position is absent also,her plug is withdrawn from its jack, whereupon the right hand switch spring of operators jack m at the left hand position engages its contact (which engagement can only be brought about by the removal of the plug attached to the operators receiver, this contact being connected to the right hand switch lever of hand switch Z and said switch lever being in contact with its left hand contact point and this contact point being connected to the right hand armature switch of pilot relay L at the next position to the left (as is clearly shown in relation to hand switch Z of the central position) the alternating current generated matically transferred to the next-position at the left in a similar way as described in relation to the right hand position.

It will be noted that as well as the audible pilot signals transferred from one position through an idle position (position at which there is no operator) to another, that any audible pilot signals originating at the said idle position are also transferred; for instance, when primary of induction. coil k of the left hand operators position is energized in a way that has been fully explained, the alternating current generated in its secondary follows a path through the right hand armature switch of operators relay M of the said position, its normal contact, right hand spring switch of operators jack m and thence through the contact it is engaged with, through the right hand switch arm of hand switch Z as hasbeen fully explained in relation to a transferred audible signalfrom the central posititon. The same being true in relation to signals originating at the right hand position. However, it will be noted that the left hand winding of pilot relay L of the left hand position is connected by line b to the live pole of grounded battery K, through commutator Qand its brush, and that the same winding of the said relay at the right hand position is connected by line It to the same pole of the said battery through commutator Z and its brush. As these commutators, by means of the varied number of their insulating segments, produce pulsations distinct from each other in the respective primaries of the pilot induction coils, the secondaries also generate alternating current of a distinct tonal quality. In this way, an operator can distinguish from the tone produced in her receiver whether the call originates at her own position or has been transferred from the right or left sections of the positions adjacent to her own.

When an alternating current is produced in the secondary of pilot induction coil h, of the central position, and the operator is busy, the audible signal is transferred in a way similar to that described in relation to pilot induction coil h only in this case, the signals are transferredv to the position at the right. The circuit for this transferred signal may be traced as follows: from the lower terminal of the secondary of induction coil k through the right hand switch arm of operators relay M, its alternate contact, left hand switch arm of pilot relay L at the right hand position, its normal contact, switch springs m and 'm. of operators relay M at said right hand position. the left hand spring switch of operators jack m and thence to' the operators receiver, or transferred to the next position if the operators plug has beenre moved, as has been hereinbefore amply described. Ifthe operator is on duty at'the .line signals assigned to her position, but that if she is busy the audible signals from the left hand half of said line signals will be automatically transferred to the position at the immediate left and if that operator is busy, will be transferred to the operators position to the immediate right of the central one. and that the reverse will happen in regard to signals from the right hand half of said line signals.

My object in transferring the audible pilot signals in that way, is' that it is easier for the adjacent position at the left to attend to the left hand half of the line signals-of the central position than it is to attend to the right hand half as well, therefore,-the signal from the latter half is sent to the position at the immediate right first and only to the left hand position in case the operator at the right hand one is busy. The reverse is naturally true in relation to the left hand position. It will be noted that the function of relay L is simply to attend to the re-transferring of these transferred signals, and that as well as being actuated by the right handwinding connected throug operators relay M, it is also actuated by the pulsatin current flowing through the primaries o operators induction coils k and h, from both the .left and right hand line signals. Therefore, as well as re-transferring a transferred signal, when the opero ator is busy completing a connection or talking to a subscriber, such re-transferring will also take place should a call originate at the position to which the call has been first transferred. Thus the calls originating ateach operators position will. take precedence over any transferred call. This is so arranged as it is more important for an operator to attend to the calls originating at her own position than it is to assist in attending to the calls at an adjacent position, the latter only being attended to when the operator would otherwise be idle.

Having now fully explained the operation of the line and pilot signals, I will explain the means used for completing a connection between two subscribers. Having heard the audible signal and observed the individual line signal of the calling subscribed, the operator inserts the answering me all armature switches of answering relay S and till plug N into the answering jaclr h: amt-- spondin to the, callin subscriber and grasps t e calling plug fi with the finger contact-device m as has already been described. This finger contact device consists of an open ring of some suitable spring meta-l lined with an insulating substance to prevent contact of the metal portionwith the finger on which it is worn, The circuit through the said tinger device on and metallic thimble n has already been traced through the winding of finger contact relay ll. lit will thus be seen that pilot relay ll, operators relay M and-finger contact relay P remain actuated as long as-the operator does not remove finger contact device m from the thimble a of calling'plug N The actuation of said finger-contact relay lP allows currenttrom' the live pole of grounded battery K to how bymeans of the brush of commutator Q, through the winding of waiting relay, lit, the lowermost otthe three top armature switches of finger contact relay l the contact thereof, the normal contact of spring switch a controlled by the top armature switchot waiting relay lit, the said spring switch to-the normal-contact of spring switch a of answering relay S, the said spring switch a, winding of answering supervisory relay T, tip of answering plug N, tip spring of spring'jacl: 1F, limb D, primary a, switch-hook a, trans- .mitter a, .limb O, ring spring of spring jack l5, ring contact 92 of answerinu plu N, spring switch 8 of answering relay its normal contact, left hand contact or uppermost armature switch of actuated finger contact relay P to the other contact of same, and thence to ground, through one-half of the divided winding of the split repeating coil U.

The actuation of supervisory relay T, due to the current flowing through the circuit [just traced closes another circuit which may be traced from ground through the winding of cut-out relay G, the'lett handwinding of subscribers message register V, thimble of answering jack 1F, sleeve contact of answering plug N alternate contact and armature switch of actuated supervisory relay T to the winding of answering relay S, where the current divides, a portion passing through said winding and supervisory lamp or signal 25 to the live pole of grounded battery K by means of talking commutator l and its brush; and a portion passing by means of the lowermost of the two upper its normal contact, the middle of the three upper armature switches of the actuated finger contact relay i9 and its-contact, the

winding of operators message register W,

switch spring in and its normal contact, l ne t?) w the i ro s s e nda l tat sry 1d,? through tang "rutator Tend its hrush i u:

The message registering system herein disclosed including both that of the operator and subscriber mayor may not he used as desired, and forms nopart-ot my present invention. "Such system, however, forms the subject of and. is-claimed in a divisional application hereofifor improvements in service meter systems for telephone exchanges, filed by me Decemberltl, 19M, Serial'hloLS'l-Sdtii. v

y The actuation of answering relay S, due to said'divided current passing through its winding, causes the uppermost of its two top armature switches to engage switch spring a before disengaging the latter from its normal contact, thus current from the left-handwinding of the grounded half of split repeating coil U replaces the current from the right hand half of the same. The lowermost of the two top armature switches of the same relay, as well as breaking the electrical-connection to operators message register W, engages its two alternate contacts, the left hand one of which bridges the connection between its winding and the sleeve of plug N previously made by means of the armature switch and alternate contact of supervisory relay T. My object in this is to avoid interruption of the current flowing through the winging of answering relay 5 by an accidental or momentary disengagement of the armature switch of supervisory relay T from. its alternate contact, it being well known in the art that the latter on account of its inclusion in the talking circuit, is of necessity of a very sensi-- tive ty e. The right hand alternate contact of the lowermost one of the two top armature switches of answering relay S being thus connected to the left hand one, closes a circuit which may be traced from the sleeve of answering plug N through the lowermost one of the three upper armature switches and its contact of calling relay 0,

tact, thimble of answering jack F and hack .to the sleeve of answering plug N. I The actuation of answering relay S, as lreFeiribeforedescribed also causes the lowermost of its twobottom armature switches to Jill through the left hand half of the split repeating coil U, for the current from commutator Q, as hereinbefore described. In this way, the armature of supervisory relay T remains pulled up, though the character of current from the live pole of grounded battery K, has been changed; however, spring switch a on being disengaged from its normal contact, engages its alternate one, thereby bridging the non-inductive resistance 27 around the winding of answering supervisory relay T. I thus provide what I hold is a new and novel means of actuating the necessarily sensitive supervisory relays connected in the talking circuit of the link connectors used in a telephone system, as the said relays are first actuated by having the full force of the operating current sent through their inductive windings, the noninductive windings being bridged across said winding after the relay armature has been pulled up; it being well known in the art that it takes but a small fraction of the operating current to hold up an armature once it has been attracted to its pole piece.

So far as has been described, the circuit of subscriber A is connected through su ervisory relay T and the two left hand ha ves of the split repeating coil U and U to the two poles of grounded battery K. When cut-out relay G operated, disengaging the line circuit of subscriber A fromthe windings of line relay H, the audible signal in his telephone receiver ceased, pulsating current from commutator I no longer flowing through the primary (1, of his induction coil. This is his signal to state the number he desires to be connected with, as the operators receiver m is bridged across the right hand halves of the split repeating coil U and U simultaneously with the operations heretofore described w 'ch connected sub-station A to the left hand repeating coil. This circuit can be traced from the right hand half of split repeating coil U, right hand contact and the uppermost of the three top armature switches of actuated finger contact relay P, alternate contact of switch spring m of operators relay M, which has been actuated as hereinbefore described, the said switch spring m, left hand spring of operators spring jack m sleeve m of operators plug, operators receiver m tip of operators plug m, middle spring of operators spring jack m condenser m, secondary of induction coil m", uppermost armature switch and contact of the three bottom ones of actuated finger contact relay P, to the right hand half of split repeating coil U By the disengagement of the innermost of the two left hand armature switches of actuated operators relay M, and the disengagement of switch spring m, from its normal contact m the audible pilot signals generated in the secalves of said ondary of induction coil It, as hereinbefore described, are out 01f from operators receiver m, as are those generated in the right hand induction coil 12, by the disengagement of the right hand armature switch of operators relay M from its normal contact. In this way, as long as an operator grasps a calling plug attached to a link connector whose answering plug is inserted in a spring jack, allowing thimble n to be in contact with finger contact device m, or in other words, is engaged in completing a connection between two subscribers, the audible pilot signals which normally affect her receiver are automatically cut oil and trans ferred to the adjacent positions in a manner already described. The same applies to the transferred pilot signals through the armature contacts of pilot relay L, the latter being also actuated. It will thus be seen that the operator can listen to the calling subscriber and talk to him without interruption caused by the audible pilot signals being actuated by other subscribers initiating calls.

When operators relay M is actuated as hereinbefore described, the various switch springs shown at the left of the same, actuate in sequence as follows: first, the innermost left hand armature switch disengages its normal contact, disconnecting the common return line m to the pilot induction coils from the middle spring of operators spring jack m tip of operators plug m and operators receiver m; second, the

outermost left hand armature switch engages its contact, closing a circuit which can be traced through it from ground, its 0011- tact, primary of operators induction coil m transmitter m, retardation coil m". to

the live pole of grounded battery K by :1

means of linek; third, spring switch m disengages its normal contact with spring switch m and engages its alternate contact, closing the circuit through the secondary of operators induction coil m, as hereinbefore described, said disengagement of spring switch m causing the latter in its turn to disengage its normal contact and engage its alternate contact. My object in thus arranging the sequence of connections and disconnections is to evade the disagreeable click in the ear of the operator when current is sent through or cut ofl from the primary of an induction coil, the secondary of which is connected in series with a receiver. ranged and described, the receiver circuit is open when current is sent through or cut off from the primary.

It will be understood that if preferred,

current could be kept continuously flowing through the primary of induction coil m transmitter m and retardation coil m", as is often done in practice, in which event relay M, could be correspondingly simplified. However, I prefer the embodiment as shown As ar- .when actually needed by the operator.

Having been informed bythe calling subscriber at sub-station A that'he wishes to talk to subscriber B, for instance, and having spoken to him, if necessary, by means of the circuit just described, the operator, still grasping the thimble 'n of calling plug N in such a way that finger contact device m is in electrical contact with it, tests the line called for by touching the thimble of one of its multiple jacks with the tip of the plug, in a manner well known to the art. (The busy tests will be described hereinafter.) If the line tests not busy, thecalling plug N is inserted in the multiple jack and thus a circuit is established which may be traced as follows: from the grounded terminal or cut-out relay G through the winding of.said relay the thimble of multiple jack E, sleeve n of calling plug N spring switch 0 and its normal contact, of calling relay 0, winding of ringing relay Y, uppermost of the two bottom armature switches and its alternate contact of actuated answering relay S, spring switch 1* and its normal contact of waiting relay R, contact and lowermost of the three upper armature switches of actuated finger contact relay P, winding of waitingrelay R, to the live pole of grounded battery K by way of waiting commutator Q and its brush; in this way, both ringing relay Y and waiting relay R are actuated. When the top armature switch of waiting relay R disengages switch spring r from its normal contact, it first remakes the connection through the winding of waiting relay R by means of its own connection to the same. However, at the same time that waiting relay R was pulling up its armature switches, ringing relay Y was doing the same and the winding of Waiting relay R is short-circuited by a circuit-which may be traced as follows: from the live pole of grounded battery K through ringing commutator Z and its brush, the lowermost of the two top armature switches of ringing relay Y and its contact, the contact and lowermost armature switch of the three top ones of actuated finger contact relay P to the top armature switch of waiting relay R, the winding of which is thus short-circuited, allowing its armature switches to fall back, whereupon the current from the contact of the lowermost of the two top armature switches of ringing relay-Y continues by way of the normal contact of switch spring. r, the contact with Which has been made by the said switch spring before the top armature switch of waiting relay R become disengaged. At the same time, cut-out relay G is actuated, removing lme relay H in the same manner as described 1n relation to line relay H, asso- .aaraegaea ciated with sub-station A, thus avoiding the display of line lamp or signal I68, when the subscriber at sub-station B removes his rece1ver from its switch hook. The central ofiice line apparatus associated with sub station B, is shown without a message register, such as shown at V, as it is one of the purposes of my invention to connect together lines which may or may not have message registers for recording calls. The actuation of ringing relay Y also closes a circuit which may be traced as follows: from ground through the ringing generator ll, continuous ringing commutator K alternate contact and lowermost of the three bottom armature switches of actuated finger contact relay P, normal contact and bottom armature switch of the short-circuited waiting relay R, alternate contact and uppermost one .of the two bottom armature switches, of actuated ringing relay Y, the non-inductive resistance i tip of plug N tip spring or multiple jack 1E limb C of line of sub-station B, call hell or annunciator a, condenser a limb D ring spring of multiple jack 1], ring contact a of calling plug N uppermost contact and armature switch of the two top ones of actuated ringing relay Y, and the right hand half of split repeating coil U back to ground. Thus an alternating turrent from generator I is at once impressed upon the line of sub-station B actuating the call bell or annunciator a without any action on the part of the operator other than the mere insertion of the calling plug N in a spring jack. The ringing current returning to ground through the right hand half of the split repeating coil 7 U, generates an alternating current in the left hand half of the same and as the calling subscribers receiver at sub-station A, and the operators receiver are both in circuit with the two halves of said repeating coil, as has been hereinbefore described, a distinct audible signal is sounded in their respective receivers assuring them that the called for subscribers bell has been properly rung.'- The ringing current impressed on the line as described is cut off as soon as the operator releases the thimble n of calling plug N from engagement with her finger contact device m, because in doing so, finger contact relay P releases its armature switches, and the lowermost of the three bottom ones disengage its alternate contact which is connected to continuous ringing commutator K and engages its normal contact which is connected with the brush of intermittent ringing commutator L The latter is connected to the brush of continuous ringing commutator K, but a large portion of its surface is insulated so that its brush only makes electrical contact with the exposed metallic portion thereof at certain intervals.

All the commutators I, Q, Z, K and M revolve at a high speed, being preferably mounted on or geared to the armature shaft of ringing generator I; but commutator L is so geared that it revolves at a slow speed, say one revolution every twenty seconds, so that if the exposed metallic segment thereof, adapted for engagement with its brush, is equal to one quarter of its circumference, as shown in the drawing, ringing current will be impressed on the line of subscriber B for a period of five seconds at fifteen second intervals. It will be obvious that by varying the size of the exposed metallic portion of commutator L or varying its speed of rotation, any desired length of ring and silent interval between rings may be obtained. As the return path to ground through the right hand half of the split repeating coil U has not been affected by the demagnetization of finger contact relay P, the calling subscriber at sub-station A will hear in his receiver the intermittent or periodic rings in the same way as he heard the first one which has been hereinbefore described.

When the subscriber at sub-station B answers by removing his receiver from its switch-hook, limbs C and D are connected together, as described in relation to substation A, the bell or annunciator a and condenser a up to this point allowed the passage of alternating current only through limbs C and D, but now the passage of direct current is allowed as well, and on this account a new circuit is now closed which may be traced as follows: from the live pole of grounded battery K, through commutator M and its brush, lowermost one of the two bottom armature switches of ringing relay Y, switch spring y, winding of supervisory relay T", tip of calling plug N, tip spring of multiple jack E, limb C, primary 0.", switch-hook a, transmitter a, limb D, ring-spring of multiple jack E, ring contact 71; of calling plug N, contact and uppermost armature switch of the two top ones of ringing relay Y to the grounded terminal of grounded battery K through the right hand half of split repeating coil U. This current actuates supervisory relay T and its armature switch closes a circuit which may be traced from the live pole of grounded battery K, through talking commutator I, calling supervisory lamp or signal t", winding of call ing relay 0, armature switch and alternate contact of calling supervisory relay T, sleeve n of calling plug N, thimble of multiple jack E, winding of cut-out relay G to ground. Calling supervisory lamp or signal t being thus displayed before the operator, she knows the calling cord is in use and that the called for subscriber has answered.

The construction of commutators K and M and their mode'of operation is peculiar. is will be noted from the drawing, the circumference of the commutators is divided nto four segments two of which are of an nsulating material, each one representing in length a little over one quarter of the clrcumference of the commutators. Alternatmg with said segments are two metallic ones correspondingly less than one quarter of the circumference of the commutators. The metallic segments of commutator K are connected to one of the armature brushes of alternating current ringing generator I, the other brush or armature terminal of same being grounded, and the metallic segment of commutator M connected to the live pole of grounded battery K. Commutator K is mounted preferably on the shaft of alternating current ringing generator I,

in such a way that its brush engages the center of one of its metallic segments when the voltage, say, of the positive current delivered to said commutator by said generator is at its maximum, the brush coming in contact with the center of the other metallic segment when one half revolution of the armature of said generator has taken place, or in other words, when the voltage of the negative current delivered to said commutator is at its maximum. of said commutator K, is in the center of each one of the insulating segments of said commutator at the exact time when there is no current being generated in the armature of the said generator I, or in other Words, when the polarity of the current delivered to commutator K is changing from positive to negative and vice versa. In this way I utilize for ringing purposes only that part of each cycle of alternating current, when the voltage is at its highest, utilizing the period represented by the rest of the cycle, for substituting direct current for the alternating one by means of commutator M, it being 'possible to send the intermittent current from the latter over a divided limb of the same circuit. Commutator M is preferably mounted on the same shaft with and insulated from commutator K and its segments are similar thereto, but it is so mounted that when the brush of one commutator is in the center of one of its metallic segments, the brush of the other is in the' center of one of its insulating segments.

On the other hand, the brush It will thus be seen that ringing current current through the said non-inductive resistance. By this means, calling superaca the ringing current, but as soon as the re-- means of actuating call bells or annunciaceiver at sub-station B is removed from its switch-hook, there is a' path for this intermittent direct current through the winding of said relay, the latter being sufliciently sensitive to attract its armature switch when energized by said intermittent direct cur rent. This I claim is a new and novel means of commutation, a new and novel means of actuating a relay, and a new and novel tors by means of alternating current,

It will be observed that means are provided whereby if the calling subscriber restores his receiver to its switch-hook before the called subscriber responds, the calling subscriber will thereby exclude the ringing generator from circuit with the called subscribers line. This is accomplished by means of the uppermost of the two bottom armature switches of answering relay S which is connected directly to the lower terminal of the winding of. ringing relay Y and which disengages its alternate and engages its normal contact when answering relay S ceases to be energized, owing to the short-circuiting of its winding by the engagement with its normal contact of armature switch of supervisory relay T,-which occurs when the calling subscriber restores his receiver to its switch-hook. The winding of ringing relay Y is thus disconnected from the live pole of grounded battery K, by way of ringing commutator Z and connected to same by way of disconnect relay P whose high resistance winding does not allow suflicient current to flow throu h the winding of ringing relay Y and the winding of cut-out relay G to maintain them in their actuated condition. In a similar way waiting relay R is denergized if the associated link connector is in a waiting instead of a ringing condition, as will be hereinafter described.

To return to the completion of a connection when the called for subscriber answers, a circuit has already been traced through the winding of calling relay 0 and its actuation causes its bottom armature switch to first make contact with spring switch 0 which turn causes spring switch 0 to break its normal contact and engage its alternate one; the disengagement with its normal contact opens the circuit of the winding of ringing relay Y, causing the latter to release its various armature switches, the disengagement of its uppermost of the two bottom ones with its alternate contact, breaking the circuit of non-inductive resistance t with intermittent ringing commutator L and bridging the former across the inductive winding of calling supervisory relay T by means of its normal contact and normal contact of spring switch 3 which is now engaged-with the latter. The lowermost armature switch of the'two bottom ones of 1 ringing'relay Y has atythe same time discontact and bottom armature switch of calling relay 0 to normal contact of spring switch 3 where it makes contact with the latter before the same is separated from its armature switch connected to intermittent battery commutator M Simultaneously with the engagement of its contact by the bottom armature switch of calling relay Q, the uppermost of the three top armature switches of the latter engages its contact thus substituting another connection to the ring.

contact a of calling plug N from the right hand half ofsplit repeating coil U, before the same is broken by the corres onding armature switch of ringing relay In this way, the current flowing through the winding of calling supervisory relay-'ll is uninterrupted notwithstanding that its current connections have been changed and as the tip and ring strands of the link connector connected to calling plug N are now connected to the two halves of repeating coil U and U conversations between sub-stations A and B can now take place. When calling relay 0 actuated it also caused its middle armature switch of the three top ones to said current flowing through n disengage its contact, thus breaking the cirthree top armature switches of calling relay 0 with its contact, closes a circuit through a calling subscribers message register, as has been already described. When switch spring 0 of calling relay 0 engages its alternate contact, it allows current from sleeve n of calling plug N to flow direct through its winding irrespective of whether the armature switch of T disengages its alternate contact, this action and the purpose thereof being the same as already described in relation to answering supervisory relay 'll. Having now explained fully the functions of the apparatus to complete a call, I will proceed to describe the procedure on the completion of the same when the two receivers are placed upon their respective switch-hooks. Each sub-station has independent control of its associated link connector apparatus, it being immaterial which subscriber hangs up his receiver first; as soon as he does so his line will test not busy at all the multiple jacks associated with his line, and if he wants another'connection' immediately, his individual line signal will respond, regardless of how many previously connected link connectors may still be in engagement with the spring jacks associated with his line. Let us say that the subscriber at sub-station B hangs up his receiver first; then the circuit for direct current is at once broken through primary 0, and switch-hook a and calling supervisory relay T releases its armature switch, disengaging its alternate contact and engaging its'normal one, by this action the winding of calling relay 0 is short-circuited, as can be seen by tracing saidshort-circuitfrom the bottom terminal of the winding of relay 0, through the normal contact and armature switch of calling supervisory relay T to the upper terminal of said winding of calling relay 0. Due to this short-circuit, said relay releases its various armature switches and as spring switch 0 disengages its alternate contact, the current from the grounded v pole of grounded battery K, flowing through cut-out relay G thimble of multiple jack E sleeve n of calling plug N and the said spring switch 0 is cut oil from the shortcircuited winding of calling relay 0 and supervisory lamp or signal t which latter thereupon resumes its normal condition. The armature switches of cut-out relay G also resume their normal condition, engaging their normal contacts and connecting line relay H to the limbs C and D of sub-station B, so that line signal 71, will again respond on' the removal of receiver a from its switch-hook. The circuit of the tip 7 strand of the link connector associated with calling plug X through non-inductive resistance t and winding of calling supervisory relay T which were multipled together by spring switch 3 of ringing relay Y is also broken by the bottom armature switch of calling relay 0 releasing its contact. The circuit of the ring strand of the link connector associated with calling plug N by means of ring contact a, is broken at the uppermostof the three top armature switches of the same relay. Thus it will be seen there is no electrical connection between the tip and ring contacts of calling plug N and grounded battery K. \Vhen the subscriber at sub-station A hangs up his receiver, the circuit for direct current is broken. as hereinbefore described in relation to the same action at substation B, and answering supervisory relay T releases its armature switch, short-circuiting the wind ing of answering relay S in the same manner as described in relation to calling supervisory relay T Answering relay S thereupon releases its armature switches and as the lowermost of the two top armature switches disengages its left hand alternate contact, the current from the grounded pole of grounded battery K flowing through cutout relay G, left hand winding of subscribers message register V, thimble of answering jack F, sleeve of answering plug N and the said armature switch of answering relay S, is cut off from the short-cirs cuited winding of the latter, and supervisory lamp orsignal It thereupon resumes its normal condition. This action also releases the armature and spring switch of subscribers message register V and the armature switches of cut-out relay G, thelatter connecting line relay Hto the limbs C and D of sub-station A, so that line signal 71 will again respond on the removal of receiver a from its switch hook. The circuit of the tip strand of the link connector associated with answering plug N, through non-inductive resistance t and winding of answeringsupervisory relay T, which were multipled together by spring switch 8 of answering relay S, is also broken by the disengagement of the lowermost of the two bottom armature switches of the same. The circuit of the ring strand of the link connector associated with answering plug N, by means of ring n is broken at spring switch .9 of the same relay. Thus it will be seen that there is no electrical connection between the tip and ring contacts of answering plug N and grounded battery K. It will therefore be seen that the talking and operating strand circuits of both calling andcalled' lines are normally open to any connection to grounded battery K.

The release ofthe armature switches of both answering and calling relays S and 0 establishes a circuit which may be traced as follows: from the live pole of grounded battery K. line is, windingof disconnect relay P normal contact and uppermost one of the two bottom armature switches of answering relay S, winding of ringing relay Y, normal contact and spring switch 0 of calling relay 0, sleeve n of calling plug N thimble of multiple jack E, winding of cut out relay (l to ground. The winding of disconnect relay I is of an extremely high resistance, for instance, 30,000 ohms, so that not enough current flows through ringing relay Y and cut-out relay G to operate the same. The actuation of disconnect relay P causes its armature switch to engage its contact, closing a circuit which may be traced as follows: from the live pole of grounded battery K through talking commutator I and its brush, line If, primary of disconnect induction coil P contact and armature switch of disconnect relay P to ground.

The pulsating current produced by talking commutator I, as hereinbefore describeih passing through its primary, generates an alternating current in the-secondary wind ing of disconnect induction coil P a circuit for which may be traced from the lower termi-' nal of said secondary, line m, normal contact of spring switch m of operators relay M, of the central position, said spring switch m whence it is led to opera'toNs-receiver m and thence to common return line m which is connected to the other terminal of secondary of disconnect induction coil P in the same manner as described hereinbefore in relation to the audible pilot signals from the line lamps. The-secondary of disconnect induction coil P transmits a signal not as loud as that transmitted by the secondaries of pilot induction coils k and h, and as all three induction coils have their primaries influenced by the same pulsating current from talking commutator I, it is obvious that the operator can easily distinguish between the two, thus knowing at once. whether to look at the line lamps or signals for a displayed one, or to look for a link connector engaged with spring jacks which displays no supervisory signals, also, should a line signal operate at the same time that the disconnect relay operates, the louder audible signal of the former would efl'ace the latter. It will also be noted that as the lower terminal of the secondary of disconnect induction coil P is connected to the normal contact of switch spring m of operators relay M, the audible disconnect signal conveyed through said contact is not transferred as are the audible line pilot signals.

Having now fully described a completed connection between two sub-stations and the automatic opening of the circuits through the link connectors used in making such connection when the receivers are replaced on their respective switch hooks, I will proceed to describe the busy tests and functions of waiting relay R which has heretofore not been described.

The described connection was made to a called for line which tested not busy; if on the other hand, at another position, a link connector was engaged with a multiple jack of the called for line and ringing current was being impressed thereon, then on applying the tip of calling plug N to the thimble of multiple ack E as hereinbefore described, or to the metallic base of a plug, should one be already inserted in said multiple jack, a circuit would have been completed which may be traced as follows: from the grounded primary m of operators induction coil m middle one of the three bottom armature switches of actuated finger contact relay P and its contact, where the circuit divides; a portion proceeding by means of the normal contact of spring switchghof ringing relayX and said spring aaa'e aoa switch, winding of calling supervisory relay T to the right hand terminal of non-inductive resistance t the other portion proceeol ing by means of the normal contact and uppermost armature switch of the two bottom ones of ringing relay Y, non-inductive resistance t, where the divided circuit is joined; tip of calling plug N thimble of multiple jack E thimble of multiple jack at the busy position, and as the link connector thereto engaged is being used for impressing ringing current on'the line, the circuit would proceed through sleeve n of plug N spring switch 0 and its normal contact of calling relay 0, winding of ringing relay Y, uppermost of the two bottom armature switches of answering relay S, its alternate contact, spring switch 7" and its normal contact of Waiting relay R, contact and lowermost of the two top armature switches of ringing relay Y to the llXG pole of grounded battery K by way of ringing commutator Z and its brush. As the said commutator furnishes a pulsating current of a nature the same as described in relation to talking commutator I, the grounded primary m of induction coil m is afiected by the said pulsating current and therefore generates an alternating current in the secondary of induction coil m which when making the test, as has been hereinbefore described, is bridged in series with operators receiver m across the halves of split repeating coil U and U Therefore, a distinct audible signal is heard by the operator in her receiver and also by the calling subscriber in his. When there are no link connectors in active use engaged with the multiple jacks of a line, then all such jacks are at the potential ofthe earth and in making a busy test no current passes through grounded primary m of operators induction coil m On the other hand, if at another operators position a link connector was engaged with a multiple jack of the called for line and calling relay 0 was'connected to said link connector, or in other words, the latter was in what I term the talking condition, then the circuit from the sleeve n of calling plug N at the busy position instead of leading to the live pole of grounded battery K by way of commutator Z and its brush, as hereinbefore described, would be connected thereto by way of commutator I and its brush, the circuit for which may be traced as follows: from 81.6%"8 n of calling plug N spring switch 0 and its alternate contact of calling relay 0, winding of said relay, calling supervisory lamp to the live pole of grounded battery K, by way of commutator l and its brush. By means of this circuit, an audible signal is heard in the operators and calling subscribers receivers, as hereinbefore describedv in relation to the busy test when ringing current is being impressed on the called for line. As commutator I has a different number of insulating segments than commutator Z, the audible signal produced in the respective receivers is of a different tone; the variation in number of the said insulating segments of the commutators being such that these two tones can be readily distinguished from each other by both the calling subscriber and the operator. (I have shown in the drawing one insulating segment for commutator Q, two insulating segments for commutator Z and four for commutator I, but it is to be understood that the number and their ratio to each other are purely arbitrary and I do not wish to be limited to the number shown.)

Having heard the talking test in his receiver, or having been so informed verbally by the operator, the calling subscriber at substation A can answer I will wait, or words to that effect, whereupon the operator would at once insert in the multiple jack E the calling plug N of the link connector engaged by means of answering plug N with the answering jack F associated with the line of substation A. WVithout any further manipulation or action on the part of the operator, the calling subscriber at sub-station A is now connected with substation B in such a way that the talking strands of the link connector connected to the lines of the latter will not be closed until the subscriber at sub-station B replaces his receiver on its switch-hook, whereupon the ringing relay Y of the link connector in the waiting condition will at once impress ringing current on the line and when the subscriber answers, the talking strands of the said link connector connected to his line will be closed and conversation between sub-stations A and B made possible. In case the called for line was being rung upon when the waiting connection was made, the talking connection will be completed to the subscriber who was first connected, and to the waiting subscriber only on the completion of same. This waiting connection is accomplished by the use of a relay which I term the waiting relay, shown at R in the drawing.

Before describing the action of waiting relay R, it will be well to state that the winding of cut-out relay G is such that it equals in resistance the windings of cut-out relay G in series with message register V, so that the resistance of the grounded thimbles of all the jacks associated with the subscribers lines is the same, whether message registers are associated with said lines or not. This resistance is such that while ringing relay Y will receive sufiicient current to operate it when connected in series with waiting relay R and one of said' grounded thimbles (as described in relation 'to the connection with a not busy line) provided no other circuit is established from' other words, ringing relay Y operates onlyv when receiving all the current from grounded battery K which is allowed to pass through the winding of cut-out relay G or windings of cut-out relay G and message register V in series. This action can easily be obtained by an adjustment of the air gap between the pole pieces and armatures of ringing relay Y, by the use ofan, adjustable spring, by the proper regulation of the winding of said relay, by a combination of these methods, or by other means, to any particular one of which I do not wish to be limited. Therefore, when the operator inserts calling plug N into a multiple jack of a busy line, a circuit is established which may be traced as follows: from the grounded terminal of cut-out relay G through its winding, thimble of multiple I jack E sleeve n of calling plug N spring switch 0 andnormal contact of calling relay O, winding of ringing relay Y, uppermost of the two bottom armature switches of actuated answering relay S and its alternate contact, spring switch 9" and normal contact of waiting relay R, contact and Y does not operate, for the reason given hereinbefore. It must be remembered that, (as has been described, when ringing relay Y operated, when calling plug N was inserted in the multiple jack of a not busy line) the winding of waiting relay R was short-circuited by the lowermost one of the two top armature switches of ringing relay Y, engaging its contact. Therefore, waiting relay R now remains actuated on account of ringing relay Y not actuating, and its top armature switch engaging spring switch 1' removes the latter from its normal contact, at the same time, the bottom armature switch'of the said relay disengages its normal contact and engages its alternate one. As commutator Q has less insulated segments than either commutator I or Z,

' any further busy tests made ;by any eperater and Z. The busy signal current thus haying a path through two of said. commute tors, the waiting busy signal is distinctive from eitherthe ringing or talking busy signals. Therefore, the o erator and an: other calling subscriber wi be advised that some one is waiting on the'line and no further connection will be made with it.

It will be seen that whentheoperatcr removes her finger contact device m. from contact thimble n of calling plug .N thus breaking the connection with :the ,winding of finger contact relay P, the only actuated relays associated with the link connector, when latter is in what I term the waiting condition, are answering supervisory relay 'li, answering relay S and waiting relay R, and that/the tip and ring connections of calling plug N which are engaged with the switch springs of multiple yack E associated with the limbs of the busy line, are completely isolated from any electrical circuit, as in order to close same, ringingrelay X or talking relay #0 must be operated and that the latter can'only be operated by means of calling supervisory relay '1, which in its turncannot be operated unless ringing relay Y has first operated. "llherefore, by limiting the operation of ringing relay Y, as has been described, ll provide means by which it is impossible for a calling subscriber, while waiting one busy line to be telephoni= cally connected thereto, or for ringing current to be impressed thereon. It will also be seen that should the operator, by mistake, connect a calling subscriber to a busy line, the action would be the same, and instead of the confusion which arises now by having three parties telephonically connected on the same line, the third party, would simply be waiting for the conversation between the first two parties connected tov be concluded.

When the .calledfor line .on a waiting connection is released in a manner which has already been fully-described, all the current allowed to pass the. winding of cut-out relay G, now flows through the Winding of ringing relay. Y of the link. connector-in the waiting condition, and it at once actuates, closing its respective contacts. Ringing current is at once impressed on the line of sub station B, regardless of the position of the brush of intermittent ringing commutator. L in relation to'the exposed metalli c,por -.v tion thereof, as the ringing circuit to latter hasbe en'zcut off, vdue to it being connected the normal contact ofthe bottom arma' ture switch; ct waiting relay ,dlt, and latter has been actuated while the link eon nector. was-inn waiting condition, it is engagedto ts, alternate contact which is connected'direct to constant ringing commutator ,KK, In this manner, instantaneously withthe replacing of the receiver on its switch-hook, if there is a subscriber waiting onthat line, the call .bell or annunciator will be operated and will continue to so operate until a subscriber answers. As the sub scriber cannothave more than removed his hand fromithe receiver when the call bell or annunciatoroperateahe will naturally remove the receiver again, whereupon the mechanismassociated with the linlr connector which has been in a waiting condition, responds, and connections to the talking conditlon are made, as has already been described. The winding of waiting is. not shortcircuited by the closing of the lowermost of the three upper armature switches of ringing relay Y with its contact, as the circuit to the upper terminal of said winding through said contact and the lowermost contact and armature switch of the three top ones of finger contact relay 1? is open on account of said relay not being actuated; the alternative path for the current from the said contacts through normal contact and spring switch r and the top armature switch of waiting relay lit being open also by the previous actuation of waiting relay R. Therefore the winding of waiting relay R can only be ,short-circuited and its A ing plug N in the multiple jack and giving u the first ringto a called for line, as has been already described. I

Elly only object in using waiting relay it is to furnish a means whereby, without any other manipulation on the part of an operator than is used in making a connection to a not busy line, a calling line canbe connected to a busy line, and that as soon as the latter becomes not busy its call bell or annunciator will immediately operate and thereafter telephonic connection made with the subscriber that has been waiting. I do not, however, limit my invention in all of its aspects to the use of this relay.

Where there are two active link connecwinding of the latter does not prevent the operation of ringing relay Y oi the link connector in the waiting condition.

when the operator made the test for a busy lineand the audible signal distinctive relay lit all to Waiting commutator Q, was sounded in her telephone receiver and that of the subscriber, in a manner which has been ah'eady described, and notwithstanding said signal (which would indicate that no other connection should be made to that line) should insert calling plug N in the spring jack; then the current flowing from ground through cut-out relay G would have three paths offered to it; to wit, the path through the link connector in the ringing or talking condition, the one through the link connector in the waiting condition and the one through the link connector by error connected to the same line, and as the adjusting means of waitin relay R is similar to that of ringing relay it is so adjusted that it will not operate when such a divided path is offered the current from grounded battery K.

Therefore, a link connector cannot be electrically connected to a line to which has already been connected another link con nector in the waiting condition.

Having described how by means of a calling plug, telephonic connection of an opera tor or third party to a busy line is impossible, I will describe how the same thing is avoided if attempted by means of the answering plug. \Vhen answering plug N is inserted in a spring jack and the thimble n of calling plug N is grasped by finger contact device an, a. circuit has hereinbefore been traced from ground through cut-out relay G and message register V, thimble of answering jack F, the winding of finger contact relay P, the said thimble n finger contact device 717], the windings of operators relay M and pilot relay L to the live pole of grounded battery K. The current so derived is sufiicient to energize the winding of finger contact relay P and cause same to pull up its various armature switches. However, if there is another plug either answering or calling, inserted in a spring jack multiplied on the same line, and if current from battery K is passing through the same, then the divided current at the thimbles of the spring jacks is not sutficient to operate finger contact relay P. The action and adjustment of said relay being the same as in the case of ringing relay Y when a waiting call is being made, as heretofore described. As no circuit is completed through the tip and ring strands of the answering cord connected to answering plug N until after finger contact relay P has actuated, it is obvious that no telephonic connection can be made with the answering plug N on a busy line.

The two arms of hand switch I at the various operators positions are arranged to move independently of each other so that the left hand switch arm can engage its left hand 'contact and the right hand switch arm its right hand contact, or both engage their right.

left hand or right hand contacts, but the left hand switch arm cannot be made to engage its right hand contact at the same time the right hand switch arm engages its left -hand contact, as in that event an audible pilot signal transferred to the ri ht would, if that position was busy, be trans erred back again to the same position it originated from. To prevent this, some such means as that shown in the drawing is used, where each of the switch arms bears an insulating buffer of the proper length to prevent the two arms from becoming 'close enough to ether to engage the two contacts mentione By means of the circuits already traced, it will be seen that if the hand switches of a position where the operators plug has been withdrawn are engaging their left hand contacts, as shown in the drawing and described in relation to the left hand operators position, then the audible pilot signals originating at that position and the transferred audible pilot signals from an adjacent position will be transferred to the next position at the left; while if the hand switches are engaging their right hand contacts, as shown in the drawing and described in relation to the right hand operators position, the same signals would be transferred to the next position to the right; while if the left hand switch arm engages its-left hand contact, and the right hand-one its right hand contact, as shown in the drawing and described in relation to the central position, then the audible signals from the left hand half of the line lamp or signals would be transferred to the left and the audible signals from the right hand half, would be transferred to the I thus provide manually operated means for transferring the audible pilot signals from idle positions, in any way that may be deemed advisable.

I have herein shown and particularly described the preferred embodiment of my invention in order that the invention in all of its aspects may be well understood, but it will be obvious that the same can be modified and simplified in many respects without de parting from the basic principles involved.

For instance, by eliminating the division of the line signals at an operators position into a left and right hand section, connected to the primaries of pilot induction coils it and It, only one induction coil would be needed, switches and contacts of pilot relay L and operators relay M could be done away with and hand switch Z simplified.

Disconnect relay P is not an essential feature of the invention, as it is immaterial whether link connectors are left engaged with the contacts of the spring jacks or not, for in practice, the operators can, when at leisure, glance at the supervisory lamps or and the right hand armature signals associated with said engaged link in,

- nected to a separate .cennehtor's', and whenever said'larnps or si nalsare not in an operated condition, they will remove the i said" link'connectorsj from engagement with said spring'jaclm. p reterred,-instead of finger contact relay P bein connected to thunble a" of calling plug 1* it could lee-connected to one terminal of a contact key-or button, and the line leading to finger contact device yn to the other terminalthus doing away with boththimble and finger-contact device and substituting a manually operated key or button.

l have shown but one battery, which furnishes current for the signal circuits, as well as thetalking circuits. However, if preferred, the signalin circuits could be conbattery. This might be a preferred plan if the battery used for the talking circuits fwas'such that the pulsatinf currents passing "through commutators Q, Z and M produced noise in the talking circuits. It a second'battery was used, it could be connected to the talking batteryv through a low resistance retardation coil, to eliminate such pulsations, in a manner well known in the art, in relation to pole changers for ringing current. ll do not wish to be limited, therefore, to the form of the invention that .has been selected to illustrate it, as changes may readily be made without departing from the spirit of the 1nvent1on'.':

It. Wlll be seen that l have provided a telephone system, including telephone lines extending to an exchange from sub-stations, jack switches in association with the telephone lines, connecting plugs attached to link connectors :tor engagement 'with said switches, a source of continuous signaling current and a source of periodic signaling current for operating the call bells or aninunciators at called sub-stations normally disconnected from the calling plug, and removing'the control of thecut-oh" relay irons;

lay mechanism individual to each link connector to control the connection of said plug to said sources of signaling current, and to remove the same under the control of apparatus at a called substation.

' It will also be seen that l have provided a telephone system including telephone lines' extending to an exchange irom substations, line signaling apparatus at the exchange for said telephone lines, connecting apparatus atthe exchange for uniting lines in conversation, a cut-oh relay governed by said connecting apparatus for preventing the presentation of the line signal of a called line or a calling line, as the case may be, and electromagnetic mechanism operable by the apparatus at'tlie called station,or calling" station, as the case maybe, independently of the apparatus of the' calling station or called station, as'thenase may'baicr re thelinle'signal oi the called line'or calling aaia aHec line and line signal apparatus and the vari'-' ous manipulations used in making a con nection, and of the operating condition of a called for line, audible signals to inform the operator that a line assigned to her position,

an adjacent position or an idle position assigned to her, is displaying its signal, and provided means to transfer said signals when an operator at a position is busy com.- pleting a connection between two other substations, also audible signals distinctive in tone quality, or loudness, to indicate whether a called for line is being rung upon, or whether a conversation is being held upon it, or whether another subscriber is waiting to be connected to it.

Y It will also be seen that l have provided a telephone exchange system including telephone lines extending from sub-stations an exchange, electro inagnetic mechanism operable by the apparatus at the called station, whether a calling sub-station can be connected to a sub-station already telephon cally connected to another in such a way that the calling sub-station willnot be telet. I

phonically connected to the one already connected until the tele honic connection therewith has first been roken, as well as various other features which together with the foregoing will be more fully pointed out in the claims;

The talking strand circuit of this system is the circuit which includes the tip and ring strands of'the link connectors and circuit connections of these strands to the i windings of the repeating coil or to'circuits controlled by the relays, individual to each link connector and involved in establishing a connection between sub-stations through said "link connector, and the; operating strand circuit is the circuit which includes the sleeve strand of the link connectors and the circuit connections of this strand to said relays, as distinguished from a strand circuit, for example, such as that of the disconnect relay which is not individual to said link connectors,

Having thus described my invention, 1 claim as new, and desire to secure by ters Patent the following:

1, A telephone exchange system, including telephone lines extending from sub-sta tion's'to "an exchange,' a visual line'signal said' exchange for each or? said lines, a source of variable current, a-circuit controlled by apparatus at a calling sub-station to impress upon its telephone-line a variable currentfrom sald source to cause said visual line signal to be energized and at the same time sound an audible signal in the telephone receiver at said calling sub-station, indicating that said sub-statlons line wires and signal means at the exchange are in operating controlled by the line relay individual thereto,

to .impress thereon a continuous pulsating current, and a circuit in branch relation to each of said visual line signal circuits and T including a winding of its corresponding line relay and the primary of an induction coil associated with the sub-station apparatus of a calling line, whereby a current will traverse said line relay which will hold its armature contact closed and at the same time sound an audible signal in the telephonereceiver at the calling sub-station by means of the connection of said telephone receiver to the secondary of said induction coil, a cut-out relay, and means under the controlof an operator and including the cut-out relay associated with the calling line to open s'aid audible signal circuit.

3. A telephone exchange system, includ ing telephone lines extending from substations to an exchange having a visual line signal individual to each sub-station, an

operators telephone set, and means common respectively to groups of said line signals to sound an audible signal in the receiver of said operators telephone set simultaneously with the operation of anyvisual lino signal in a corresponding group.

l. A telephone exchange system, including telephone lines extending from substations to an exchange having avisual line signal individual to each sub-station, a telephone receiver normally associated with a group of said signals, and means under the control of apparatus at a callin sub-station to send a continuous pulsating current through said visual line signal and thereby impress an alternating current on the operating circuit of said receiver.

A telephone exchange system, including telephone lines extending from.- substations to an exchange having a visual line signal individual to each sub-station, a line relay individual to each of said signals-for controlling the same, anoperators tele: phone set, means contrQlle'd by said line relays to impress a continuous. pulsating current-on the operating circuit of corresponding visual 'line signals, and means also controlled by said line relay to impress an alternating current on the operating circuit of an operators telephone receiver.

6. A telephone exchange system, including telephone lines'extending from sub-stations to an exchange having a visual line slgnal associated with the line of each ofsald sub-stations, an operating circuit for each of saidvisual line signals including a source of variable current, a telephone receiver assoclated with a group of said visual line signals, whereby said variable current- 1s caused to produce an audible signal in' said receiver, on the operation of one or more. of said visual line signals in said.

oup. 7; A. telephone exchange system, including telephone lines extendingfrom subual thereto and including a source of current, commutating means for impressing said current on said circuit in continuous pulsations, the primary of an induction coil, and a circuit including the secondary of said induction coil adapted to .sound an audible pilot signal in an operators telephone receiver.

8. A telephone exchange system, including telephone lines extending from sub-stations to an exchange having -a visual line signal individual to each sub-station, a telephone receiver for each operators positionat said exchange, a pilot relay for each such position, a source of variable current, an operating circuit for each of said visual line signals including said source and a winding of said pilot relay, an operators relay for each-of said positions, a circuit controlled by said operators relay and including said telephone receiver, whereoy said variable current will sound an audible pilot signal in said telephone receiver, on the operation of one or more of said visual line signals at a corresponding position. v

9. A telephone exchange. system including telephonellines extending from sub-stations to an exchange having a visual line signal individual to each sub-station, a line relay individual to each sub-station, an o erators telephone set for each operators position, a pilot relay individual to each operators position, an operating circuit for each of said visual line signals and controlled by the line relay of the corresponding sub-station, each of said circuits includtion therefor to automatically transfer said audible pilot signal to an operators telephone receiver at an adjacent position and if said second operator is occupied in the same way, to re-transfer said audible pilot signal to another operators position adjacent to the first, and means operating on the receipt of any pilot signal originating in an operators position to automatically out 01f the transfer to that position of said signals from an adjacent position and to automatically re-transfer them to another position.

16. A telephone exchange system, including telephone lines extending from sub-stations to an exchange having a switchboard provided with a visual line signal individual to each sub-station, an operators telephone set at each operators position provided with a jack plug adapted to engage a spring jack at each of said positions, and means common respectively to groups of said line signals to sound an audible pilot signal in an operators telephone receiver simultaneously with the operation of any of said visual line signals in a corresponding group, and means operative when a given operator is engaged in communicating with a calling sub-station or completing a connection therefor to automatically transfer said audible pilot signal to an operators telephone receiver at an adjacent position and if said second operator is occupied in the same Way, to re-transfer said audible pilot signal to an operators telephone receiver at another operators position adjacent to the first, and if any of said operators telephone receiver jack plugs are withdrawn from their respective spring jacks, to transfer said audible pilot signal to the next adjacent operator whose said jack plug is engaged with its spring jack, and means whereby the signal transferred to either operators position adjacent to the one first receiving it is of a different character from the audible pilot signals originating in said adjacent operator's position, and means operating on the receipt of any pilot signal originating in an operators position to automatically out off the transfer to that position of said signal from an adjacent position and to automatically re-transfer them to another position.

17. A telephone exchange system, including telephone lines extending from sub-stations to an exchange having a switchboard provided with a. visual line signal individual to each sub-station, an operators telephone set at each operators position provided with a jack plug adapted to engage a spring jack at each of said positions, and

means common respectively to groups of said line signals to sound an audible pilot signal in an operators telephone receiver simultaneously with the operation of any of said visual line signals in a corresponding group; and means operative when a given operator is engaged in communicating with a calling sub-station or completing a connection therefor to automatically transfer said audible pilot signal to an operators telephone rcceiver at an adjacent position and if said second operator is occupied in the same way, to re-transfer said audible pilot signal to an operators telephone receiver at another operatorsposition adjacent to the first, and if any of said operators telephone receiver jack plugs are withdrawn from their respective spring jacks, to trans for said signal to the next ad acent operator whose said jack plug is engaged with its spring jack, manually operated switches at each operators position for determining the direction of said transfer from said position in which said jack plug is withdrawn from its spring jack, and means whereby the signal transferred to either operators position adjacent to the one first receiving it is of a different character from the audible pilot signals originating in said adjacent operators position, and means operating on the receipt of any pilot signal originating in an operators position to automatically cut off the transfer to that position of said signal from an adjacent position and to automatically re-transfer them to another position.

18. A telephone system comprising in combination with sub-station lines an exchange switchboard therefor having a plurality of operators positions, means initiated at a sub-station for producing a pilot signal at an operators position, and means individual to said position and controlled by the operator thcreat to cause said substation means to instantly produce said pilot signal at another of said operators positions, and automatic switching means at said positions, whereby on the disconnection of an operators telephone receiver from its operative connection, said pilot signals are instantly produced at another operators position.

19. A telephone system comprising in combination with sub-station lines an exchange switchboard therefor having a plurality of operators positions, means initiated at a sub-station for producing a pilot signal at an operators position, means individual to said position and controlled by the operator thereat to cause said sub-station means to instantly produce said pilot signal at another of said operators positions, automatic switching means at said positions. whereby on the disconnection of an operators telephone receiver from its operative connection, said pilot signals are instantly produced at another operators position, and manually operated switches at said positions for selecting the position at which said pilot signals shall be produced.

20. A telephone exchange system, includllO 

